text:
How were astronomical observations performed from Concorde?
In addition to passenger flight and charter flight, Concorde has been used for astronomical observations, including the longest solar eclipse observation on 30th June 1973(PDF) and observation of Halley's Comet on April 1986.

How was Concorde modified for astronomical observations?
How is safety ensured with equipment installed when flying at supersonic speed and at 60,000 feet?

In 1973, it was a Concorde prototype, flown by André Turcat, a test pilot. Some information (in French) about this F-WTSS 376 flight.

It does seem to be the convention 'round these parts to warn people of a PDF link (mostly for the mobile users, I would think). Especially since that link does not show it's a PDF when hovering the mouse.

The Concorde was first used for observing solar eclipse in 1973. The aircraft used was Concorde 001, piloted by André Turcat with a scientific team of 8 people from US, UK and France.
The main reason for using Concorde was that the eclipse can be observed above the clouds for far longer than on ground by literally 'chasing the moon'. Multiple instruments were used for observing the eclipse.
Institut Astrophysique de Paris used cameras to capture images of the eclipse using a telescope mounted on anti-vibration mounts, which looked out of the aircraft through one of five silica quartz windows installed in the Concorde's roof. The equipment is shown in the image below:

Source: xjubier.free.fr
Queen Mary College's InSb Far-Infrared Detector experiment consisted of an interferometer that used a tracking mirror to view the solar eclipse via a quartz window fitted into the roof of the cabin, as shown in this image.

Source: jcgl.orpheusweb.co.uk
The dark opening in the roof holds the quartz window of the cabin, which looks like this:

Source: xjubier.free.fr
This was the most important (structural) modification made in the Concorde (BAC was supposed to provide Concorde 002 for this flight, but they backed out when they realized that some holes were to be made in the roof).
Los Alamos Scientific Laboratory (LASL, later to become Los Alamos National
Laboratory) used a specially-designed 3-inch telescope which looked out of the
aircraft through a silica quartz windows installed in the Concorde's roof. One objective of the research was to look for oscillations in the sun's corona that occurred on a time scale of about five minutes (the eclipse was visible for ~74 minutes from Concorde).
The instruments were checked both in ground and air before the experiment.

Before installation of the instruments on the aircraft, they were tested on a low speed trolley, perhaps to check its sensitivity to movement.
After the ground test, they were installed on the aircraft and connected to the aircraft power system and checked.
Before the actual experiment, the aircraft were flight tested at supersonic speed with the instruments on board.

The Concorde was chartered for viewing Halley's Comet in 1986 and for viewing solar eclipse in 1999. These were chartered sightseeing flights (using unmodified aircraft), not scientific ones.

Is it just me, or does that last image (of the dark fitting around the hole in the roof) have small flashes of white appearing in it? I see them in the blackest part, clockwise from about 190° to 10°.

This SO question addresses it, but that doesn't seem to be the case here (as far as I can tell).

@FreeMan, that SO question is definitely not relevant here, the image is static. I suspect you are actually noticing the quantum noise of the weak light (I see that pretty well on anything dark) or some other artefact of the way eyes work (I don't remember them, but there are some).

May be monitor specific. I don't see it at home.


text:
What is the angle between A330 body and the ground?
Since the standard A330's nose-down body angle on the ground, the A330F uses a revised nose undercarriage layout to provide a level deck during cargo loading to overcome the issue.
What is the angle between A330 body and the ground?

Another interesting, and related question would be: why does the passenger version have a nose-down angle? I understand why they want the freighter to have a level cargo hold. But why the nose-down angle to begin with?

TL;DR The angle is about 1 degree.
The best reference I can think of is the aircraft characteristics document provided by Airbus. This provides key dimensions for the A330 family.
I looked at the dimensions for the forward and aft lower deck cargo doors. The document provides both the distance from the ground to the floor of the hold (§2-3-0), and to the door center from the nose (§2-7-0). With this information, an inverse tangent will give the angle of the deck between the doors.
There are two factors that affect these numbers. First, the three models of aircraft have different measurements. The other factor is weight and balance of the aircraft, which affects how much the suspension on each gear is compressed. A heavier aircraft will sit lower to the ground, and the location of the center of gravity will affect how much weight is resting on each landing gear position.
Calculating the angles gives the following angles. Note the larger angle on the shorter -200, and the difference of about a degree between the values on the -200 and the freighter -200F.
Although 1 degree may not seem like much, note the difference of about 33 cm (13 in.) height between the -200 and the -200F at the forward cargo door. This is near the nose gear, which is the reason that modifications were necessary to fit the extra nose gear length in the gear bay.
-300

176,000 kg, CG 26.8%: 1.2 deg
MRW, CG 15%: 1.1 deg
MRW, CG 36.5%: 0.8 deg

-200

119,000 kg, mid CG: 1.4 deg
MRW, CG 21%: 1.3 deg
MRW, CG 37.5%: 0.8 deg

-200F

115,000 kg, CG 20%: 0.4 deg
MRW, CG 20.6%: 0.2 deg
MRW, CG 37.4%: 0 deg

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text:
Can construction of an airport lead to more foggy weather?
The following paragraph is from Wikipedia "Airport" page with no citation.

The construction of airports has been known to change local weather patterns. For example, because they often flatten out large areas, they can be susceptible to fog in areas where fog rarely forms. In addition, they generally replace trees and grass with pavement, they often change drainage patterns in agricultural areas, leading to more flooding, run-off and erosion in the surrounding land

Is that bold statement true?

Hmm... This seems like it would have rather the opposite effect. It's usually harder for fog to form when there's nothing to break the wind and easier for it to burn off in flat areas, where hills and trees don't provide shade when the sun is low on the horizon.

The statement is apparently from the Introduction to Airports Design and Operations of
Center for Air Transportation Systems Research at George Mason University.
One form of fog that is formed in airports usually is radiation (or ground) fog. As the flat open surfaces in airport are prone to cooling overnight due to thermal radiation, the air close to the surface is also cooled to the dew point. This reduces the ability of the air to hold moisture, allowing condensation and fog to occur.
One reason for the statement may be that open areas in the airport give up their heat much quicker than urban heat islands, which does not have flat surfaces prone to thermal radiation.

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text:
Does a private pilot certificate require a certain number of ground school hours?
To obtain a private pilot certificate in the US you need a minimum of 40 flying hours. Is there a minimum of ground school hours? Or is it just however long you need to pass the test?

For training conducted under 14 CFR 61 there is no requirement for groundschool.  The only requirements are that you take and pass written tests, but how you prepare for them (formal groundschool, self-study, etc) is completely up to you.  You will need a recommendation from a flight instructor to take a written test, so your preparation method and readiness for the test will be evaluated before you are allowed to take it.
The only exception to the above statement is knowledge tests for airline transport pilot certificates with airplane multi-engine class ratings taken after 31 July 2014.  These written tests do require specific groundschool training minimums, which are specified in 14 CFR 61.156

If you are instead training under 14 CFR 141, your school has a specific curriculum and examination authority approved by the FAA.  The specifics of your program will dictate what groundschool is required to take the relevant written exams.  The groundschool aeronautical knowledge baseline requirements are specified in 14 CFR 141 Subpart F.  For a private pilot certificate with an airplane category rating, these requirements are:

35 hours groundschool training in

Applicable Federal Aviation Regulations for private pilot privileges, limitations, and flight operations;
Accident reporting requirements of the National Transportation Safety Board;
Applicable subjects of the “Aeronautical Information Manual” and the appropriate FAA advisory circulars;
Aeronautical charts for VFR navigation using pilotage, dead reckoning, and navigation systems;
Radio communication procedures;
Recognition of critical weather situations from the ground and in flight, windshear avoidance, and the procurement and use of aeronautical weather reports and forecasts;
Safe and efficient operation of aircraft, including collision avoidance, and recognition and avoidance of wake turbulence;
Effects of density altitude on takeoff and climb performance;
Weight and balance computations;
Principles of aerodynamics, powerplants, and aircraft systems;
If the course of training is for an airplane category or glider category rating, stall awareness, spin entry, spins, and spin recovery techniques;
Aeronautical decision making and judgment; and
Preflight action that includes—

How to obtain information on runway lengths at airports of intended use, data on takeoff and landing distances, weather reports and forecasts, and fuel requirements; and
How to plan for alternatives if the planned flight cannot be completed or delays are encountered.


text:
What keeps an aircraft engine from flaming out at high altitude?
High altitude atmosphere has lower oxygen level. How do aircraft, especially the military ones, prevent engine flameout?

See here for an answer.

High altitude atmosphere has lower oxygen level. No, it doesn't.

The air is more thin higher in the atmosphere, but the oxygen level does not decrease in the atmosphere just the air thinness and pressure.

I think what he meant was that the partial pressure of oxygen decreases with altitude, which it does.

The oxygen level at high altitude is the same as at sea level, namely 20.95%. What is lower is the oxygen pressure.
To avoid flameout, pilots must avoid to throttle the engine down too much, so a minimum pressure in the combustors can be maintained.
Designers can increase the altitude performance by building longer combustors. The speed of ignition is pressure dependent, and with lower pressure it takes longer for the fuel-air-mixture to ignite. More length allows more mixing and leaves the mixture more time to react. Also, they can add flame holders which leave pockets of burning fuel close to the injection nozzles, so the mixture is heated more rapidly and ignites more reliably. Normally, flame holders create drag and are reduced to the minimum necessary.

Throttle up or down? I assume down but I have no time in jets.

@egid: I think "throttle" is usually used as a synonym for the verb "limit"? I don't think I've ever seen it as a synonym for "relax"/"increase"/etc.

@Mehrdad that's true, but in aviation, the throttle is the control for how much power the engine delivers. I've heard it verbed as "throttle back", down, up, etc.; it seems to be more useful with a modifier. Limit in this example doesn't make sense either, fwiw: "pilots must avoid to limit the engine too much".

@egid: Huh, okay.

@egid: Mehrdad's understanding is correct (the context was probably helpful), but I agree that clarity of this sentence can be improved. Edited.

@egid, most descriptions I've read insisted that turbines don't have anything called ‘throttle’. They have ‘power’ levers in turboprops and ‘thrust’ levers in jets.

@JanHudec: Isn't the action of moving those power levels called throttling (up or down)?

At high altitude, aircraft engines have a number of built in safeguards to prevent flameout, like,

The engine igniter is on continuously. This continuous ignition is set automatically by the FADEC if flameout conditions are detected.
In case flameout occurs, the FADEC tries to restart the engine automatically (in response to loss of thrust, for example).
The engines also have compressor bleed valves, which serve to prevent compressor stall in case a sudden increase in thrust is demanded from the engine.

Also, as Peter says, at high altitude, the percentage of oxygen remains the same, but the partial pressure is less.

Better answer IMHO as it actually answers the question as it was asked. +1ed


text:
Can the HAL Lca Tejas perform Pugachev's Cobra maneuver?
Can any variant of the HAL Lca Tejas (either the naval variant, the mark 1, mark 2 or later) perform Pugachev's Cobra?  If not, why?

Please clarify - do you mean this aircraft?  https://en.wikipedia.org/wiki/HAL_Tejas

Yes, of course!

No.
With that delta wing shape it will have pitch control problems at higher angles of attack. The Cobra maneuver requires a small pitch-down moment over the post-stall region up to 110° angle of attack. I very much doubt that this wing planform will have such pitch characteristics, and without thrust vector control a docile pitch behavior is a prerequisite for the Cobra maneuver.
In the development of the LCA a high lift coefficient without leading edge devices was the main goal of the wing design. It should be able to operate in the vicinity of flocks of birds - birdstrike is a real risk on many Indian Air Force bases. At the same time, the small aircraft should be able to fly supersonically, which lead to the double-delta wing as the best way to achieve both goals, and poor post-stall pitch response had to be accepted.
When HAL switched from MBB to Dassault for technical support, leading edge devices were added in order to fulfil the take-off and landing requirements. Post-stall flight was not seriously considered at any point in the development.

You are genius!

Clear and lucid explanation, Thank you very much for your precious time!

I read here that it does have thrust vectoring.

@TomMcW I've read it too but cannot find a second source. The nozzle on Tejas pictures looks awfully conventional to me, so I suspect the AFTech writer has got it wrong.

No known variant of the HAL Tejas can perform the Cobra Maneuver.
This is for the simple reason that the aircraft was not designed nor was it expected to perform such a maneuver.
In a Cobra, the plane suddenly raises the nose to the veritical position (or beyond, usually 90$^{\circ}$ to 120$^{\circ}$) before dropping it back to the normal flight, maintaining more or less the same altitude through the entire maneuver.

Source: www.saddahaq.com
The cobra maneuver is a dynamic maneuver to a high angle of attack, beyond any equilibrium or trim point. Pitching angular momentum carries the aircraft to a peak angle of attack.
According to Airplane Stability and Control,

The Cobra is started from unstalled flight with a rapid application of full nose-up control, which is held up to the maximum angle of attack point, about 90 degrees. Control is neutralized for the recovery, assuming that the airplane has a negative or nose-down pitching moment at that point.

As can be seen from above, the performance of this maneuver requires control (and a pitch down moment at high aoa) in the high angle of attack region, though it can be done with conventional controls.
The Tejas is not designed with such characteristics. The main thrust in designing of Tejas was to get a 4(+) generation aircraft with relaxed static stability. Tejas is basically a replacement for Mig-21 (a process which is not going very well), and as such the main design goals were to produce a small, supersonic aircraft to excel in interception/air superiority role.
Towards this, the compound delta wing was chosen because it was small and lightweight compared to other designs available. Though the wing has good high-alpha characteristics and aircraft has good maneuverability, post-stall maneuvering was never considered for this fighter. As such, no variant of Tejas has the capability to do post-stall maneuvering and there are no plans to include them in the future.


text:
Would it be practical that nuclear-powered seaplane (only flying low over the sea) or hovercraft can be an alternative to cargo plane or ship?
Would it be feasible that nuclear-powered seaplane (only flying very low over the sea) or nuclear-powered hovercraft can be an alternative to cargo planes or ships? The aircraft speed can reach 200 mi/h like a propeller plane and the container-sized Small Modular Reactor will be possible. So goods could be shipped from China to the US within a week at a relatively low price.
It may be a competitor to cargo planes or ships.

The flying height of this aircraft is only one or two hundred meters.
Flying only over the sea and can landing on the sea.
And the speed is low. It can be safe enough.
Container-sized Small Modular Reactor can be under 100 tons.

After @GdD commented, I got this Ground-effect vehicle.
Edit:
Would fuel-cell-powered Ground-effect vehicles like Boeing_Pelican be a competitor to cargo planes or ships?
Comments
I'm a Chinese guy and I'm interested in amateur radio and always watching some videos on YouTube. Recently I've watched a video about introducing some cheap handheld radios made in china. The YouTuber mentioned that waiting for the shipping from China for 6 weeks. So I thought there's maybe a demand for Speeding up the shipping at a relatively low cost. And so I think the nuclear-powered seaplane may be a choice in the future.

Related: Why don't aircraft use nuclear propulsion?

You mean like this: https://en.wikipedia.org/wiki/Lun-class_ekranoplan ?

@GdD Yeah, thanks. I'm really thinking about this kind of thing, but I don't really know.

Why do you assume a lower speed is safer? Generally speaking, being low & slow is where an aircraft, aerodynamically speaking, is most vulnerable

@expeditedescent Yes, being low means weather is a big factor. And being slow means avoiding hitting against the water rapidly in an emergency.

Does this answer your question? Why don't aircraft use nuclear propulsion?

While this question is overly broad and so fails on that score anyway, one of the many reasons this wouldn't work is that nuclear power isn't suitable for any aircraft, even a ground-effect vehicle. Hence the proposed duplicate. I'll note also that a flying height of 100-200 m doesn't put the vehicle in ground-effect anyway, unless the proposed aircraft will be significantly larger than the largest viable airplane so far. So there's that too. Besides the nuclear issue, there're other good reasons large ground-effect vehicles didn't work

There is a long list of other issues as well, but in order to avoid a too long post I stuck to adressing the points you made in the question.
As with most other things this boils down to the economics. If we assume that the technical challenges can be resolved and you're able to build something that fly according to your description, it will still cost a lot to develop and build. But how much does it cost to carry a full load from A to B compared to the other options, and how long does it take?

It may be a competitor to cargo planes or ships.

Ships are great for freight because they carry a lot of stuff at once cheap but slow. Aircraft are great because they go fast and high, and are less impacted by weather, but at a higher cost while carrying less.

The flying height of this aircraft is only one or two hundred meters.

One of the advantages of existing aircraft is that when something go wrong, you can trade altitude for time to troubleshoot. Flying at a few hundred meters means less time to troubleshoot; being powered by a nuclear reactor means that you will need a lot of redundancies to minimize catastrophic system failures. You'll also be more exposed to weather, which will increase the stress on the airframe compared to other aircraft.

Flying only over the sea and can landing on the sea.

This will expose you to more salt water, which will drive both R&D costs to make the aircraft more resistant to corrosion, but it will also increase maintenance costs in the long run.
Landing and taking off from water is harder in bad weather or at night. A land-based plane can usually count on having runway lights available, and a firm surface to land on. A seaplane has neither but will be affected by waves in addition to wind.
This will also limit the routes you can fly, and therefore also the potential customers for this plane.

And the speed is low. It can be safe enough.

Flying slow will make you less able to avoid bad weather; flying around it might not be possible before it overtakes you. While in theory you could be able to land instantly in case of problems if the cruise speed is close enough to the landing speed, you'll still have weather to contend with.
Crashing at 200kph isn't automatically safer than at 800kph. Using nuclear power will limit which countries would allow operations, as one crash would be enough to destroy an entire area.

Container-sized Small Modular Reactor can be under 100 tons.

This is less than the fuel weight of a 747-8F even if you add engines. According to this question electrical engines are likely to weight around twice as much as comparable turbine engines, so with a bit of goodwill and a lot of assumptions we can replace the engines and fuel load of a 747-8F with a reactor and 8 engines.
Even if this were to work, I suspect the maintenance costs would be huge, and you wouldn't really solve a problem. Chances are you'd go slower than existing aircraft but at a higher price and with a less reliable timetable.

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text:
Is flap down the same as flap extended to 25degrees?
Is Flap down command is same as setting the flap angle to 25degrees. Recently I am reading the information related to Flap and got confused with different terminology. Trying to get relation between flap angle and Down/Up commands. On the same line I read that EGPWS uses the flap down signal, and why EGPWS need this signal.

It isn’t clear to me what you are asking.  Most aircraft, even simple GA airplanes, have several different angles they can be set at.  So, for example if the flaps were up, you could command them down to 10 degrees, or 25 if there was such an increment on your airplane.  I don’t know what this has to do with EGPWS other than the tone might be inhibited with flaps down under the assumption that landing is intended.  What specific airplane are you asking about?

Hi @MichaelHall, just trying to understand the impact of flap signal on EGPWS behavior and at the same wanted to get my self clarity on what angles are flaps down and up. Thank you for the information. Now I got clarity.

Hi @ManuH I corrected the tittle, thanks for pointing that out.

Thanks, I was able to discern that from the answer.  Freeman is smarter than me!

Depending on the aircraft, flaps can be set at one of several different settings anywhere from 5° to 40° (or more, from what I understand). All of these settings are considered "down". (The exact flap angle depends on the aircraft, current weight, air temp and other factors and more than one is "appropriate" for take off or landing depending on these conditions.)
The EGPWS (Enhanced Ground Proximity Warning System) needs to know whether flaps are up or down (among other things) so that it knows if the plane is configured for landing. If you're 50' AGL and configured for landing, the EGPWS is going to assume that your intent is to land, so it won't tell you "pull up". If you're not configured for landing, but you're still 50' AGL, it's going to yell at you in an attempt to keep you from flying into the ground.

Thank you @FreeMan for the answer, this clarified my doubts.


text:
What is the role of an intermediate fix?
There are the IAF and the FAF, which has clear roles. One is where you start the approach and the other where you start to descent and end the approach. But what is the purpose of an Intermediate fix?

How is IAF, the Intermediate Approach Fix, different than "Intermediate fix"?  Do you have a chart example showing both?  I think that there are approaches where the IAF is overflown at one altitude outbound, then one circles back and descends inbound to cross the same point as the FAF.

The IAF is meant to be the Initial Approach Fix. Or am i wrong? Please do correct me. Added a picture.

Oh, that's right, "Initial" Approach Fix. I am out of practice!  As the chart shows, the IF is between the IAF and the FAF, and is a tracking/reporting point after the holding pattern. Might be a mandatory reporting point, or you may be asked to report when getting there.

Here is an explanation that I read and I liked the most as I think it better explains the role of the intermediate segment and thus the intermediate fix. Skybrary in the IAP page mentions:

Intermediate approach segment - this segment usually begins at the intermediate fix (IF) and ends at the final approach fix (FAF) or final approach point (FAP). Here the aircraft speed and configuration should be adjusted to prepare for the final approach. For this reason, the descent gradient is kept as shallow as possible.

Emphasis is mine as up until that point there is nothing new. Checking the ICAO Doc 8168 PANS-OPS cited by Skybrary, in Chapter 4 INTERMEDIATE APPROACH SEGMENT paragraph 4.1.1 we read that

The intermediate approach segment blends the initial approach segment into the final approach segment. It is the segment in which aircraft configuration, speed, and positioning adjustments are made for entry into the final approach segment.

In addition to all the elements in JScarry's excellent answer, intermediate fixes can also be used to step down altitudes, such as during the ILS 10C at Chicago O'Hare.

This is probably the most succinct answer to the OP’s question ie “what is the purpose of an IF?” as opposed to “what is an IF?”

The Pilot/Controller Glossary can shed some light on your question.
The GPS approach is the clearest example of an Intermediate Approach Fix.

IF/IAWP− Intermediate Fix/Initial Approach Way- point. The waypoint
  where the final approach course of a T approach meets the crossbar of
  the T. When designated (in conjunction with a TAA) this waypoint will
  be used as an IAWP when approaching the airport from certain
  directions, and as an IFWP when beginning the approach from another
  IAWP.
INTERMEDIATE APPROACH SEGMENT [ICAO]− That segment of an instrument
  approach procedure between either the intermediate approach fix and
  the final approach fix or point, or between the end of a reversal,
  race track or dead reckoning track procedure and the final approach
  fix or point, as appropriate.

The Instrument Flying Handbook warns that, “Randomly joining an approach at an intermediate fix does not ensure terrain clearance."
On other approaches, there may not be an intermediate fix, but the segment is defined as follows:

INTERMEDIATE FIX− The fix that identifies the beginning of the
  intermediate approach segment of an instrument approach procedure. The
  fix is not normally identified on the instrument approach chart as an
  intermediate fix (IF).
INITIAL APPROACH SEGMENT [ICAO]− That segment of an instrument
  approach procedure between the initial approach fix and the
  intermediate approach fix or, where applicable, the final approach fix
  or point.

The Instrument Flying Handbook also talks about intermediate fixes where there is sometimes a charted Intermediate Fix:
Teardrop Procedure

When a teardrop procedure turn is depicted and a course reversal is
  required, unless otherwise authorized by ATC, this type of procedure
  must be executed. [Figure 1-15] The teardrop procedure consists of
  departure from an IAF on the published outbound course followed by a
  turn toward and intercepting the inbound course at or prior to the
  intermediate fix or point. Its purpose is to permit an aircraft to
  reverse direction and lose considerable altitude within reasonably
  limited airspace. Where no fix is available to mark the beginning of
  the intermediate segment, it shall be assumed to commence at a point
  10 NM prior to the FAF. When the facility is located on the airport,
  an aircraft is considered to be on final approach upon completion of
  the penetration turn. However, the final approach segment begins on
  the final approach course 10 NM from the facility.

Holding in Lieu of Procedure Turn

A holding pattern in lieu of a procedure turn may be specified for
  course reversal in some procedures.  In such cases, the holding
  pattern is established over an intermediate fix (IF) or a FAF.


text:
Which single pilot jet has the largest cabin and longest range?
I'm looking to rent a jet for a trip round the world with my friends but also since I have my license and MEIR, I'll be able to fly myself and don't want to hire another pilot.
Which single pilot jet has the largest cabin and longest range?

How many hours of single pilot business jet experience do you currently have? I doubt you will find anyone to rent you a business jet just because you have a MEIR.

@MikeSowsun I have 1700 hours of flying a single pilot business jet (Embraer Phenom 300) and 7000 hours of commercial flying (A380 and B777).

According to Wikipedia's list of light jets, the longest ranges (for single pilot certified jets) are:

SyberJet SJ30: 2205 NM
Pilatus PC-24: 2035 NM
Embraer Phenom 300: 1936 NM
Cessna Citation CJ4: 1927 NM
Cessna Citation CJ3+: 1825 NM

Sorting by max. number of passengers, we get:

Pilatus PC-24: 8-11
Embraer Phenom 300: 7-10
Cessna Citation: 8-9
SyberJet SJ30: 5-6

Considering you are already rated for the Phenom 300, this is likely your best option. Anything larger will always require a minimum crew of 2.

I don't like the size of the Phenom 300. Lovely jet to fly, but I'd much rather get a type rating for something else rather than fly it round the world with friends since it's cabin is a bit too small. The Pilatus PC-24 seems to be what I'm looking for so I'll most likely go for that. Thanks!

Please let us know how you do finding a Pilatus PC-24 to rent because I would like to do the same thing!

@MichaelHall did you ever manage to get a rental for it?

@Eros, no… my comment was tongue in cheek because I agree with others that you won’t find one for anything other than a long term lease.

@MichaelHall Thanks for taking the time to reply to my question! It is in fact hard to rent for a couple days one of those. More so being just a regular person and not a company. Too much risk for the owners of the aircraft being damaged or stolen.

Well the Phenom 300 currently qualifies under this.
But without an ATP ME with a type rating in the Phenom and employment with said charter firm as a pilot, no one is going to rent the thing to you as a pilot and let you fly it.  It’s not like a rental car.


text:
For how long are state and federal aircraft registrations valid?
How long is a state registration valid for and how long is a federal registration valid for?
and for state I mean North Dakota if any of you know where to look for that.

State registration depends on the state. In Wisconsin, it is required to be renewed annually. Some states do not require registration.

California doesn’t have a registration system per se, but we pay property tax on the aircraft each year, so if you own an aircraft you are "registered" with the state.

Cheers thanks guys !

Federal registration is for three years, according to the FAA (the actual regulations are in 14 CFR 47.40):

Aircraft registration issued due to renewal expires three years from the expiration date of the previous certificate.
Aircraft registration issued to a new, import, or reinstated aircraft entering or re-entering the U.S. Civil Aircraft Register
  expires three years after the last day of the month in which it is
  issued.

State registration - if any - is up to each state so you need to check with the state where the aircraft's owner registered it.

Cheers thanks for that


text:
Where are the seaport conventions for VFR charts explained?
VRF charts contain information about seaports. For example, 00 - 50 in the formation block for HNL seems to be for a waterway:

Another example is 23W for 1C9:

Where are these conventions explained? I can't seem to find them in the Legend or User Guide.

This question is very similar, and this answer answers your question.

"00 - 50" means a landing surface at 00 feet MSL, unlighted, and 5000 feet (nominal, 4970-5069 actual) long.
At aerodromes with both land and water surfaces, it is customary to suffix the water ones with "W" (pronounced Water, not Whiskey) to avoid confusion.

Do you have a reference for the W suffix? I found a reference about 00 - 50 on page 16 of the Aeronautical Chart User's Guide.

@rvernica I've never looked for a reference, sorry.


text:
What are the strategies for getting familiar with a GA aircraft before considering a purchase?
Looking over the comments and answers in this question got me to thinking: How does a new pilot get familiar with the large variety of GA aircraft when contemplating a purchase?
Initially there's a vast number of aircraft to even be aware of—for example, I'd never heard of a Citabria before today. So I suspect it would be easy to overlook the perfect aircraft by virtue of simply never having a chance encounter with it. I suppose the answer to this is to attend airshows and fly-ins.
Then obviously some considerations can be satisfied with light research, such as seating and performance characteristics. But outside of that, once you have a short list, how does a pilot go about getting a "test drive"..?
Like so many before, I'm presently learning in a 172. Afterwards, though, I'd be interested in getting endorsed for a low-wing. A nearby FBO offers training in Piper Arrows—but what if I was curious about flying a Mooney, or a V-tailed Bonanza ..or a ..Citabria?? :) How do the Mooney pilots get their first flight in one??
I'm mostly interested in light, single-engine models, and I realize this question is rather conversational, but I'll appreciate any insights.

There are lots of ways to go about this.
Rent: as you have mentioned nearby FBO's have various planes although they are almost always Pipers (Warriors, Arrows, occasionally a Saratoga or Lance) or Cessnas since those are common trainers. You may also find a light twin here and there as well as a Grumman or something like that. In this case you can rent what you want to try and go up with an instructor.
Friends: As you fly more you will meet people at the airport. Often times these are plane owners and they have a whole variety of stuff. Eventually people may offer to take you out for a flight in their plane (which will be way better maintained than a lot of trainers). If you tell someone you are interested in purchasing the same make and model they have, they may be more inclined to take you up. You may also meet other people who are training in a different plane than you. For example, I fly the Warrior and Archer at my school and another student who I have become friendly with flies the 172. Since we are not check out in the other planes respectively and we are about at the same point (close to our check rides) Im sure we will fly with each other in the respective planes in the future.
Flight Clubs: A lot of local airports have flight clubs that sometimes own a nice variety of stuff and you may be able to meet a member and have them take you up to show you around what ever it is they have, you may even be able to join the club and get checked out in their planes.
Internet: The internet is abuzz with forums for just about every big maker out there. Some are free and others are super cheap to join if they cost anything at all. You can often times find local owners on these forums who may be willing to take you up or at least show you their plane. You would be surprised how hard it can be to find people to fly with sometimes.
Dealers: Much like cars new planes come from dealers. You can always try your local dealer (although Im not sure if they will take you up) I would think they would at least let you sit in the plane. There are dealers spread across the country but if you can rent a plane now you can always fly to them (Piper, Cessna, Mooney)
When You Buy: When (if) you buy a plane you will need to insure it. Generally insurance companies will require time in type to get the insurance. You can sometimes agree upon mandatory instructor time in the plane you just bought before you fly it solo. This allows you to be able to buy just about any plane and not have a ton (if any) time in it.
Finding Strange Planes: When (if) you go to buy a plane you will define your mission. After doing so you will begin to talk to people about what you want and you will get plenty of suggestions on what to buy that fits your mission.
Strange Planes Are Strange For A Reason: I can only assume you are training (or have your PPL) and are thinking about getting a plane. To this I will offer some advice I have been given. Planes are no small item to own, fiscally, legally, and simply physically, they require a lot of space. There is a reason the common models are common. They fit a lot of missions, are generally reliable, easy to fix and get parts for as well as easy to fly. While I lust for a Mooney M20 Acclaim Type S the truth is (money aside) I am no where near ready for a 200+ knot plane that is nothing but slippery. Remember to respect the machine.

Sounds pretty similar to the process for buying a car, but with higher altitude.

Yep this is about what I expected. And you raised a good point about the costs of ownership—the more common the aircraft, the more routine the maintenance and cheaper the repair/replacement parts.


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Will wind tunnel modelling ever be completely replaced by computer models?
With computer-based fluid simulation already being extremely realistic (and likely faster and cheaper than physical wind tunnels), are they, anywhere, completely replacing physical wind tunnels? If not, is this planned anywhere, or even possible?

This question is quite subjective, you might consider editing it to include your specific question and you previous research over this topic

How do you intend to validate the computer models? A wind tunnel is most helpful for this.

@PeterKämpf how do you validate wind tunnel model?

This question is very specific and not subjective.

This question is speculative and may not be answered without a strong part of personal beliefs about technologies' futur

@TrebiaProject. isn't the standard practice, as far as there may be a 'standard' something like computer modeling, wind tunnel testing of physical models, testing of full size models? What I mean is Wind Tunnel will be validating computer models, not the other way around. actual physical testing of models/mockups (wings, engines, planes, etc) would seem to be less overall expensive done in a wind tunnel where everything is controlled, then going straight to full size testing. (IANAE)

@CGCampbell corrections on wind tunnel are commonly computaed by numerical simulation. I found a reference in the first googling: http://www.nasa.gov/sites/default/files/643655main_Wall_Interference_Overview.pdf . My point is, there are simplifications in both models and they are commonly used for crosschecking each other.

@TrebiaProject.: First, you measure the flow field in the tunnel thoroughly. Next, you run the simulation with the tunnel parameters. Tunnel corrections are for things like flow distortion, tunnel turbulence and differences in Reynolds and Mach number. Most of that can be avoided when the computer model models the wind tunnel directly. When the tunnel simulation works at all Mach numbers, the computer model is also fit for bigger Reynolds numbers than those of the wind tunnel model.

@PeterKämpf that works for the wind tunnel flow input. More concrete example, how do you correct the pressure measurement taking into account the effect of the support of the model creates on the surface? As well, how you correct the balance output of the global force?

Keep in mind that both CFD & wind tunnel results may not work in the real world. Just ask any Formula 1 team that shows up to a race weekend with new aero parts that just don't work on track like they did in the tunnel or on the computer. I realize there are likely some complexity differences, but issues can remain.

@TrebiaProject. You model the model including its support, wind tunnel walls and whatever is there which influences the flow. Just compute what you see and can measure.

@PeterKämpf which essentially means, that you use the computation to validate which part of the wind tunnel result is correct. Actually, you can obtain differences to apply to the model due to support interaction. Which comes back to the previous statement, in some areas you use part of the results of the simulation to validate results in wind tunnel and corrects them.

The thing about computer models is that they are just that; models. They can only approximate the actual behavior we see in the real world.
Computer models are good for trying many different ideas and making predictions. It can be faster to create a new computational test than to make a physical model for a wind tunnel. But very detailed fluid dynamics calculations require large amounts of computing power, and this takes time and money as well.
Wind tunnels can give much more detailed and accurate information, and are useful for validating the results given by the computers. The results don't always match, which means that the computer models must be revised. This is where wind tunnels are still very useful. They can test an entire airplane in actual flow, where computing that detail across the whole aircraft would require long computations.
Although a wind tunnel is also only a model of real conditions, it provides an actual body in actual flow conditions, which means the results can correlate much more closely to the real conditions being tested. Computational analysis is limited by assumptions, the chosen modeling method, and computational power.
Until computing power reaches the point where it can run models that will truly match a wind tunnel's accuracy and detail, there will still be a need to use wind tunnels to provide data.

I remember seeing something on NASA TV about testing this concept, and they said the wind tunnel performance was better than the models predicted.

the problem is not computing power, although is part of the picture. Still wind tunnel is accurate. And finally... simulation is far more detailed.

The thing about wind tunnel models is that they are just that; models. They can only approximate the actual behavior we see in the real world.

At the end we are taking about modeling, where we are having computer modeling and on the other side we have hardware modeling. When we are talking about modeling we have 3 levels of modelization:

Geometry and external conditions modeling: approximation made of the geometry and the external conditions defined in the problem. This includes the supports created in wind tunnel for example.
Numerical discretization: how the external flow domain is discretized numerically.
Turbulence modelling: how the external physics is represented (Euler, RANS, LES...)

Hardware modelling is only affected by the first parameter, for example, Reynolds number is not the same in many wind tunnel. Tests and the external conditions are replaced by walls. In fact, in the area of geometry and external conditions, numerical simulation is far more advanced than current WTT state of the art.
Numerical discretization is only present in numerical simulation, and here just by adding brute force you can reduce is as much as you can. Current state of the art is not allowing to reduce it to 0.
Turbulence modelling is the key for numerical simulation. Current models used in the industry are not able to properly model some extreme areas (high separated flows for instance) and the current most promising techniques (DNS, LES) are highly demanding in computational time, increase constrains in the discretization area and, more importantly, have not been proved properly on industrial relevant cases.
You can see that current numerical simulation is ahead to wind tunnel (hardware simulation) in the area of geometry and external conditions, but mainly weak on the area of turbulence modelling.
Current situation is that wind tunnel has been replaced by numerical simulation in the area where turbulence modelling is not highly demanded by accuracy demands or physics complexity.
However, for being able to model some part of the physics the industry can only go hardware testing (wind tunnel).
Going more precisely to your question, numerical modelling will replace hardware testing when is able to solve the gap in turbulence modelling. The current situation as I described above, there are some approached promising to the future, but we will be able to evaluate if those approaches (DNS, LES) are able to close the gap when an application of a full aircraft is made. Currently, that is foreseen in 20 years time (I don't have reference sorry...), my point of view is that 20 years is optimistic.
So answering your question is, we can answer the question yet, we need 20 years further to be able to answer you.
Finally I would like to make a point in terms of costing. It is clear than creating a model in hardware testing (a phyisical model) is much expensive than a model in numerical testing (a mesh). However, a model in a wind tunnel has a huge productivity once in a wind tunnel (a new simulation point in less than a second), simulation takes hours once the model is ready. However, numerical simulation is reducing each year the cost of its model much more faster than wind tunnel. Still for some applications with high productivity of points needed, wind tunnel is far cheaper.


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Do LED lights work well for CAT III B operations?
Does any airport equipped with LED lights for all the CATIII B Components? If so, is there any history that it caused difficulty in aircraft operations?
We are planning to install our new runway with CAT III B lighting with LED fitments.

You have a lot of questions, you might condense this down into a single question.

Can you make this question more about one thing? Just because you are asking about CAT III B lights, doesn't mean all questions related to that can be added together in a single one.

Will do that, thanks for the comment

I don't know if you can do Cat IIIB with a HUD (I'd have said that you're limited to Cat IIIA with one, but somebody may have a capability I'm not aware of) but no, LED lights generally don't wash out a HUD any worse than other lights do.  If your HUD brightness is sufficiently dim, then bright enough lights of any sort can wash it out, but that just requires you to turn the brightness up a bit.
I've never heard of or seen any "Sea of Blue" effect from LED lights, and I don't think LED lights have particularly worse glare (or any other) characteristics when used as runway lighting.  They're somewhat distinctive, but not particularly worse.
If LED lights have regulatory approval for what you want to do, I'd say that right there is the answer to your questions.  And if they don't, well, then that's also an answer.


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Why does the 747 have 4 engines instead of 2?
If the 747 can fly with two engines, why does it have four engines?
What is gained by adding another 2 engines?
Flights over the ocean?
Fuel savings?
Safety?

Please, edit your question to make it more clear. Are you assuming the B747 can fly with only two engines? It cannot take-off with only two engines.

Because it can't fly with only one engine?

@MichaelHampton Actually, it can... if the engine happens to be a GE90-115b.

Because six would be just silly.

But five is not? They are built for that.

@DeanF. It could carry a fifth engine but just as cargo, it wasn't operative.

@PerlDuck - in the spirit of 6 being silly, 5 is still silly, but possible and done for a reason. The extra engine is mounted under the wing like a working engine. It is just not connected to run/operate. They use this technique to transport spare engines when necessary. Sort of like when you mount a spare tire on the back of your car. On some cars (jeeps, classic cars, off-roaders,) it looks great. On other cars, it’s just plain silly looking.

@DeanF. Indeed. See https://aviation.stackexchange.com/q/24181/18733

Simply, more engines = more power, and power is needed for several things, the first of which is, taking off.  At max takeoff weight, a multi-engine aircraft has to be able to lose one engine (after reaching the go/no-go speed) and safely continue the takeoff, which means that if you could just barely fly on 3 motors, you're going to have to have 4 to meet certification (safety) requirements.  For the amazing weights that the 747 can carry, it needs some pretty powerful motors, and all 4 of them, for taking off fully loaded and meeting this requirement.  (Interestingly, if the aircraft is empty and could safely continue the takeoff on 2, it is typically allowed to take off with one engine already inoperative -- to ferry to a maintenance base, for instance.  But this requires no passengers/freight, and thus a very light airplane.)
At cruise altitude, more thrust means a higher cruise altitude is possible, which makes for better fuel efficiency.  So while a 4-engine aircraft can certainly fly on 3 engines, and in many cases (depending on weight and outside air temperature) on 2, it can't fly as high as it could with all 4.  The higher cruise altitude not only makes for more efficient flight, it also keeps you above a lot of the weather out there, and in extreme cases, a 2-engine ceiling might not clear all the terrain on your route.  (Again, this depends on weight & temperature.)
Modern engines have amazing reliability, and it's now considered routine to dispatch the twin engine 777 and 767 and A330 on long overwater routes, but 50 years ago, the reliability wasn't as great, so it was considered essential to have the redundancy so that if one engine failed over the middle of the ocean, there was still a comfortable margin, and you weren't now "one motor away" from going swimming.

I would presume that the engines the 747-100 launched with were also less powerful per unit than the ones being built and installed on the 747-8, 777, 767, A300, etc today.

@FreeMan You are correct, the original engine was the JT9D-3A putting out 45,800 lbs of thrust. When I stopped flying 747s in 1999, we had the JT9D-7 series which put out in the neighborhood of 56,000 lbs. Also Rolls Royce and GE engines were coming on line with higher thrust levels. The first 747-100 I flew had a max takeoff weight weight of 735,000 lbs, the last 747-200 I flew was up to 825,000 lbs. 747-400s are up to at least 875,000 lbs now. Be aware this is all from the memory of a 76 year-old subject to senior moments.

Two engine aircraft are now routinely flying routes that when the 747 came out were illegal to fly with only two engines. It's a sobering thought to me when I board one that we're starting out with half the engines gone. At least it's still illegal for a two engine airplane to take off with one engine inoperative. I jest, of course.

@Terry Wikipedia says 833,000 lbs MTOW for a -200 but agrees with every other number you wrote. Sounds like the memory's ticking along just fine!

@Terry, even if a couple of numbers are off, I love hearing your stories and anecdotes! Fascinating stuff!!

In addition to what Ralph mentioned, up until the mid 1980s, regulations required that aircraft operating long over-water routes or other such routes with a lack of places to divert in the case of emergency must have at least 3 engines. Specifically, this applied to any route that was more than 60 minutes from a diversionary field in areas subject to FAA regulations and 90 minutes in other places. The planes used on these routes during that era consisted of 4-engine aircraft like the De Havilland Comet, Boeing 707, Douglas DC-8, and Boeing 747 as well as 3-engine aircraft like the McDonnell Douglas DC-10 and Lockheed L-1011 TriStar. These regulations were due to engines historically not having been nearly as reliable as they are today. This was especially true of the piston engines used before the jet age, but also of early jet engines.
So, to specifically answer your question, in order to serve the long-haul trans-Atlantic and trans-Pacific routes for which the Boeing 747 was intended, it was required to have at least 3 engines. Boeing apparently decided it preferred to go with 4 and keep them all wing-mounted. This also didn't require as much thrust output per engine, making the engines easier to design, especially at that time.
However, by the 1980s, jet engines had become sufficiently reliable and powerful that a new class of regulations called ETOPS (previously "Extended-range Twin-engine Operational Performance Standards," now "ExTended OPerationS") was developed to allow twin-engine aircraft to fly overseas routes, provided they met certain standards. The first aircraft certified for such operations was the Boeing 767, which was allowed to fly trans-Atlantic operations for TWA. Its initial ETOPS certification allowed the 767 to fly up to 90 minutes away from a diversionary field and this was later increased to 120 minutes after TWA had demonstrated success with the 90-minute certification. However, the original ETOPS regulations still limited aircraft to a maximum of 120 minute ETOPS on entry into service and 180 minute ETOPS was only allowed after at least a year of successful operation with 120 minute ETOPS. As such, aircraft designed during this period for long-haul operations, especially trans-Pacific, such as the MD-11 and Airbus A340, still went with 3-engine or 4-engine designs. Unfortunately for Airbus and McDonnell-Douglas, those aircraft were released right around the time the FAA began allowing 180 minute ETOPS at release.
The newly-developed Boeing 777 was the first aircraft to qualify for 180 minute ETOPS at entry into service. Largely as a result of the efficiency it gained by having only 2 engines, the 777 trounced the A340 in sales, leading the A340 program to an early death. Shortly thereafter, Boeing acquired McDonnell Douglas and ceased production of the MD-11. With the 777 now allowed to fly, not only trans-Atlantic, but also trans-Pacific routes, the need for tri-engine or quad-engine jets to fly those routes vanished. The 777 was then followed by the A330, 787, and A350 in being able to serve those routes. Each of these programs has been very successful, however, their success has largely resulted in the imminent death of the tri-engine and quad-engine models of the past. The A340 has stopped production entirely. The 747 and A380 have had scant new orders over the last few years, leading to the possibility of both programs being cancelled. According to Wikipedia, as of the end of May, the A380 has had no new net orders so far in 2015 and the 747 has had only 3 (and none in 2014.)

The 747 began life in the mid 1960s, as an alternative to the Boeing 2707 SST. To hedge their bets, the 747 was designed to be converted to a freighter as well. Hence the bulge at the front and the top mounted cockpit - to facilitate a front opening cargo door. When the 2707 was canceled due to cost overruns and rising fuel prices, Boeing fortunately had the 747 well under way.
At that time, gas turbine engines were limited in power output. The 747 was the first large scale commercial application of high bypass turbofans, a fairly new technology. To meet the power needs of an aircraft with the 747's weight and carrying capacity, four engines were required. They were also required for long over ocean flights, to insure that the aircraft could make landfall in the event of a loss of an engine... gas turbines in the 60s weren't as reliable as they are today.
Once the design is set, altering it later to change to two of the new very large gas turbines that came out in the 90s would have been prohibitively expensive. Simpler to design a new large airliner with two engines in mind: the 777.

As stated before, back in the days- the aircraft characteristics and the thrust certification of the engines demanded the aircraft design to include 4 engines in order to conform with the different regulations of ETOPS and various engine loss scenarios that can be encountered during any phase of flight.
Looking at the statistics we can see that during the last 30! years, around 15 passenger aircraft (meaning- airlines) were forced to make a gliding landing due to various reasons.
Of these aircraft, none was due to a Dual engine failure that was caused by a technical malfunction. Most were because of fuel exhaustion, some due to pilot error (shutting down the incorrect engine after a malfunction) and 2 (recently) due to bird strikes. This leads to a conclusion that a 4 engine aircraft would not be immune to the dangers which led to the forced landings of the noted above, maybe except for the bird strikes- but it is very hard to make a statistical assessment of the risk due to various components of the encountered flocks, sizes and patterns of the birds.
The engines today are super reliable (as of 2019 there are some problems with the engines of the 787's but they are addressed as we speak) and one can deduce that having more engines actually brings more chance for fault, thus nowadays it is safe to say that the main consideration for aircraft design and number of engines is the final weight of the aircraft and the amount of thrust needed in order to meet all the specified gradients of climb and of course reaching a relevant airspeed in order to take off on most runways of the world which are limited by length or obstacles.
By the way- while losing 1 engine in a dual-engine aircraft can be challenging, but losing an outer engine on a 747 during takeoff results in a huge yaw asymmetry, making it even more challenging due to the distance from the center of the aircraft.
So, theoretically speaking- there is no reason for the B747 to have 4 engines. They would have to be bigger than the GE9X in order to carry it, thus leading to a re-design of the aircraft which practically has no justification. If the airlines found that it can be more profitable to run all planes on 4 engines (including risk assessment, investment and wear cost)- we would have been seeing more and more of those flying.

Good answer, but dive deeper into the span loading and thrust line advantages of 4 engines.  The "twins" are still working to resolve these issues today.  The B-52, flying at a higher altitude, still does fine with 8.

You have to remember the era in which the aircraft was designed.  The engines weren't as powerful so they needed four to get airborne and four to fly long haul over-water routes. There are engines now that could do the job in pairs but the 747 would need to be drastically redesigned because among other problems the wing is too low to accommodate the monster engines on planes like the 767 and 777.  What Boeing should reconsider was an aborted 3-engine design like a big 727.  They looked at it once back in the 60's but the engines weren't there yet.  Now would be a good time to reconsider.

The 777 engines could be tested on the 747 but were a bit of a stretch. The 767, however, uses the same engine types as the 747-400.

Why would Boeing want a 3-engine aircraft when a 2-engine aircraft will suffice? Boeing did have a 3-engine airplane back in the 90s - the MD-11, which they acquired from McDonnell-Douglas, but they stopped production of it, since they didn't really do anything that couldn't already be done with a 747, 767, or 777.


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Why does the length of the 737 vary so much?
The longest version is almost 50% longer than the shortest, and even within the "next generation" models, the difference is almost 40%.  Why such a big difference in lengths?

different designs, it's easier to vary a design than start from scratch

Airlines want to have different sizes of aircraft to match their passenger loads as well as possible. The different loads may be for different routes, times, or airlines. It is more efficient to fly a smaller plane if extra space isn't needed.
Aircraft manufacturers have some options for how to meet this demand. They can create a whole new airplane for each size, but this is expensive for everyone involved. Each plane would have to be certified separately, requiring much more time and testing. They may not be alike, requiring pilots to be trained on each individual one. And airlines would have to maintain all the different types of airplane.
Instead, aircraft manufacturers choose to stretch the fuselage to fit in more passengers. This can allow most other things on the plane to remain the same, with generally just minor modifications. This greatly decreases the amount of design and testing required to create the new size of aircraft. The same pilots and mechanics can work on any of the sizes, since most parts and features are common to all of them. There will be some inefficiency, in that parts on the small versions are designed to withstand higher loads of the bigger versions, but this is more than offset in the cost savings of having common parts.
Most aircraft come in different versions with different lengths, but it can be most noticeable on the smaller planes like the 737.
The manufacturers also market their products based on their coverage of different seat capacity. Each manufacturer is able to cover a wide range of seat capacity by offering different sizes of 3 basic models.

Source

On a side note, the differently-sized variants usually have the same main type number with exception of A318/A319/A320/A321 where the main number varies.


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Are regulations covering private jets different from those covering commercial jets?
Do private jets have relaxed FAA regulations (and regulations imposed by any other aviation agency) when compared to commercial jets? If yes, which aspects of aviation are these relaxations are pertaining to?

Where do you draw the dividing line between "private" and "commercial" jets, or are you just referring to operational requirements?

Private jets : Jet being used for personal use ( Not considering the charter jets provided by commercial companies for use by individual on lease)

FYI, businesses use private jets as well, and it is not for personal use, but for business use. Generally speaking, the line between private and commercial flights is whether or not they are for compensation or hire.

Technically no, but in the spirit of your question, yes.
All aircraft, including those operated for private and commercial purposes, are governed by 14 CFR 91 - General Operating and Flight Rules.
14 CFR 119 specifies additional regulations that govern certain types of aircraft and operations, including larger private aircraft and commercial operations:

14 CFR 125 covers larger (airline style) private aircraft
14 CFR 121 covers the airlines
14 CFR 135 covers commuter and on demand (charter) commercial operators

So it isn't that private aircraft have relaxed regulations, it is just that they aren't required to comply with the additional regulations that govern the airline and charter operators.
There are many, MANY additional regulations that commercial operators have to comply with, including operational and maintenance regulations.
A few example:

Pilots flying commercially have strict limits on the time that they are allowed to fly or be on duty.  Pilots of private aircraft don't have any limit, other than not to fly if it would be unsafe.
Commercial pilots are subject to more strict medical requirements.
If an aircraft has to divert due to a mechanical problem, it must be reported to the FAA if being operated commercially.
There are strict limits on how far that a commercially operated aircraft may be from a suitable airport, but there are no such limits for privately operated aircraft.
Passengers must be screened and must be checked against government maintained no-fly lists for commercial flights.
An aircraft used for commercial purposes is required to be inspected more often.
With certain (very limited) exceptions, commercial aircraft are required to be operated by a company (certificate holder) with required management personnel such as the Chief Pilot and Director of Maintenance, while private aircraft can be managed by one person (even the pilot).

See the online eCFR for the specific regulations that fall under each part.

Depending on what you are looking for:
Here and here are the requirements for operating as an air carrier. All air carriers from the large airlines to the smaller charter situations must follow the same rules so to speak. The rules generally draw the line at accepting/paying money to fly or be flown in an aircraft respectively (as I understand it).
If you own a large jet aircraft (fully or fractionally) take a look here for more information on how that's governed.

§91.501   Applicability.
  (a) This subpart prescribes operating rules, in addition to those prescribed in other subparts of this part, governing the operation of large airplanes of U.S. registry, turbojet-powered multiengine civil airplanes of U.S. registry, and fractional ownership program aircraft of U.S. registry that are operating under subpart K of this part in operations not involving common carriage. The operating rules in this subpart do not apply to those aircraft when they are required to be operated under parts 121, 125, 129, 135, and 137 of this chapter. (Section 91.409 prescribes an inspection program for large and for turbine-powered (turbojet and turboprop) multiengine airplanes and turbine-powered rotorcraft of U.S. registry when they are operated under this part or part 129 or 137.)

In the end of the day it falls on the pilot in command to make sure that their aircraft is airworthy.
If you hone in a bit more on a specific question you would like answered we can try to aid you.
There are some varying certifications for specific smaller jets that allow them to be operated a little differently than a commercial airliner. The vast majority of commercial jets require 2 pilots however there are smaller jets like the Citation Mustang that are certified for single pilot operations and geared mainly towards the private jet crowd. So that might be what you are looking for, but that's the only one I can think of off hand.


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When is the logo light on the tail turned on?
I noticed sometimes aircraft taxi with the logo light illuminating their tail, while others have it off. So is turning on the tail light at the discretion of the pilot?

There can be several lights on the empennage (tail section) of an airplane. There are two as shown here:

Image Source
The red light is called aircraft beacon. The white light is called strobe.
When to turn them on is explained here:

All aircraft built after 11 March 1996 must have an anti-collision
  light system (strobe lights or rotating beacon) turned on for all
  flight activities in poor visibility. The anti-collision system is
  recommended in good visibility, where only strobes and beacon are
  required.

Another one is logo light:

This light illuminates the livery design on the vertical stabilizer.
For more details, please see this question:
When to use Beacon, Anti Collision, Strobe, Logo and Navigation lights?


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How do airports charge airlines for using their gates?
I'm wondering how the airports charge an airline for using a gate or a parking spot (if they use buses). Does the airline have to pay per time or per "event" or do the larger airlines have fixed gates for which they pay a yearly rent?
Could you elaborate on what systems there are and when they are used? How much are the costs?

this things are usually covered on non-public agreements between airlines and airports.

It's called landing fee. There are many factors involved and it varies from airport to airport, airline to airline and country to country.

@Farhan I think landing fees are typically just the fees paid for landing, not for renting gates/jetways/stands/ticket counters/baggage claims/etc.

@reirab Please see the article I referenced: Landing fees may encompass additional airport provided services.

Overview: The Airport Business from ACI, Very complete answer: Chapter 4 of The Airport Business book by Rigas Doganis.

@PeterKämpf I think you meant to @ mins, not Rigas Doganis...

@mins: Thanks for the link, that is actually very interesting. If you paraphrase the Doganis chapter into an answer, you will get my upvote.

@raptortech97: Thanks, of course. Not my day today ...

Gates are usually not charged to airlines separately. Gate fee is usually part of the landing fee package. Landing fees are an important part of the airport revenue, with passenger fees.
Airport pricing is subject to recommendations from ICAO, IATA, and other organizations, as regard scope of costs to be taken into consideration, and non-discrimination of airlines. Pricing is determined by the organization managing the airport and/or State or local administration.
Single till vs dual till: Distinguishes between aeronautical and non-aeronautical (commercial) charges. Airport schedule pricing may use single or dual till. See: Single till - IATA.
ICAO Policies on Charges for Airports and Air Navigation Service. ICAO guidelines tries to maintain some principles for airport business across all countries:

Landing charges: Should be based on the aircraft weight formula. The maximum certificated take-off weight as indicated in the certificate of airworthiness (or other prescribed document) should be used, while considering local restrictions that may affect aircraft maximum take-off weight. Allowance should be made for the use of a fixed charge per aircraft or a combination of a fixed charge with a weight-related element, in certain circumstances, such as at congested airports and during peak periods.
Parking and hangar charges: For the determination of charges associated with use of parking, hangar and long-term storage of aircraft, maximum permissible take-off weight and/or aircraft dimensions (area occupied) and length of stay should be used so far as possible as the basis.Any period of free parking time for aircraft immediately following landing should be determined locally by considering aircraft scheduling, space availability and other pertinent factors.
Other charges:
-- Passenger service charges
-- Security charges
-- Noise-related charges
-- Emissions-related aircraft charges

Albeit a bit old, The Airport Business by Rigas Doganis has a chapter on Aeronautical charges and pricing policies which discusses this topic in depth. Extracts:

Landing fees: Charged per aircraft, usually based on MTOW (maximum takeoff weight). On most airports covers ATC, runways, taxiways, parking at stand or apron for a certain time (e.g. 2 hours), use of gates / fingers / terminal for disembarking (use for departure may be paying), take-off.
Surcharges or rebates in addition of landing fees: For noise, peak-hour operations,
Parking and hangar: Beyond the free-parking period covered by the landing fees. Usually based on weight.
Passenger charges: per departing passenger, sometime per arriving passenger too.

It is easy to find pricing for airports online.
Adelaïde airport (2015)

Rates are different for domestic and international flights.
Charges per passenger for landing and passenger facility.
For domestic flights, additional landing charges per ton of MTOW.
Charges for diversion.
Parking charges beyond 2 hours, paid per arrangement with airport.

New York LaGuardia (2015)

Charge for aircraft landing, per thousand pounds of MGLW (maximum gross landing weight).
Additional charge for day landing or takeoff (not for schedule airlines).
Charge for using public passenger ramp and apron area (in some cases, when congestion).
Charge for parking and storage, per 8-hour slot, based on MGTOW (maximum gross takeoff weight). Agreement possible for operators of aircrafts.
No charge for air terminal use.
Charge for each passenger departing.

Los Angeles Intl (2013)

Landing fee, based on MGLW, different between permitted and non-permitted air carriers.
No charge for remote gates bussing service.
Charge for using ramp, apron and remote area, (in some cases, when congestion).
Charge for parking, per 1000 lbs of MGLW, per day, after 3 hours.


text:
How are the limits of the center of gravity chart established?
When one views a center of gravity limit chart, in this case a C-182T chart, one notices that the forward C.G. line has two small bends in it, one around 2250# mark and the other around the 2675# mark. Why the two bends in the forward C.G. limit line? What has happened at these two points?

Image from: C-182T POH pg. 211

Could you perhaps add an image or a link to the chart in question?

I think it's likely that the limit actually curves but the engineers decided to make straight lines out of them in the manual so pilots could interpolate them better.

Correct me if I'm wrong but the area presented by a deflected control surface is the tangent of the angle of deflection (opposite side of "triangle"). The increase of area presented is linear to the angle of deflection.  Coefficient of Lift is also linear with increased AOA, so yeah, they may be actually straight.

These "bends" (or sloped straight lines) are due to various structural constrains on the aircraft.

In level flight, the sum of forces must be zero:
LiftWing - Weight - LiftTail = 0
The summation of moment should also be zero, otherwise the plane will pitch up or down.
The wing has a structural limitation, i.e. a maximum loading. Solving the above equations for constant LiftWing yields a slopped straight line. This is the "bend" portion you see in the graph.
Drawing these lines (shown as colored lines here) on top of a weight and balance graph yields:

The resulted graph is the intersection of the various constraints.
In the C-182 graph, there are five constraints (five edges). Wing loading and tail loading is used as an example here, since I do not know what is the actual constraint used by the engineers. Another possibility is strength of the nose gear.
Main landing gear loading and aft tipping limit would have resulted in a downward slope, which does not correspond to the given graph.

Source: Center of Gravity Limitations (PDF)

Interesting information, but it doesn't describe why there are two distinct kinks in the graph for the C182, which is what OP asked.

@FreeMan I have edited the answer to relate to the OP's graph. It was already in the answer, but might not be very clear.

I'll take your word for it.  ;)  That graph looks like it's got about 8 dimensions, and even after 4 semesters of calculus (a looong time ago), my brain doesn't want to wrap around it. Don't worry about me, though. If others are having difficulty, more explanation, if it's just me, let it go.

Are you sure it's not about limiting stick forces??? If you post speculation, please spell out clearly that you are guessing.

@PeterKampf limiting stick force would be mathematically equivalent to limiting tail loading.

@kevin: Mathematically, yes. Unless you include pitch trim. Now set pitch trim and try to maneuver the aircraft without exceeding stick forces. To make sure that enough control margin is left, the cg position must be limited. Tail loads can vary a lot for the same stick force. BTW: The wing and tail load limits line are much more shallow than the limits in the Cessna 182 chart.

@PeterKampf: I didn't say the graph is to scale, or did I?

There could be two reasons:

Performance: The more forward c.g. location demands more speed, so the wing can create enough lift to counteract the downforce from the tail. To keep the minimum speed below the 61 knots mandated by FAR part 23, the forward c.g. location at high gross weight needs to be restricted.
Stick forces: A more forward c.g. location translates into bigger elevator deflection angles for maneuvering. Again, the airworthiness requirements put lower and upper limits on them, and it could be that the upper limits are exceeded with the combination of high gross weight and forward c.g. location.


text:
Are there any examples (real life cases) of invalid FMS data affecting flight operations?
Do you know of any real life cases, when invalid FMS data affected somehow the flight operations?
By invalid FMS data I mean a case, when the procedure coding does not reflect properly the original procedure as published by state's AIP service.
Related question: What happens with RNAV procedures on the way from AIP publication to FMS database

Here is some old material used in Europe to prepare for the transition from AIS to AIM: AIS to AIM: Enabling the Net-Centric Information Environment by Roderick van Dam, Head of Eurocontrol Legal Service. The document references two legal cases where navigational data and hardware were involved.
Pakistan International Airlines

Bejon v. Pakistan International  Airlines (Toulouse Court of
  Appeal, 1998) Liability of Jeppesen raised.  Jeppesen argued that
  approach map  was based on map provided by States.  Court concluded
  that map was  technically acceptable This case confirmed  the risk
  related to  the publication of Aeronautical data.

More: PIA Flight 268.
American Airlines

American Airlines v. Jeppesen- Anderson and Honeywell (US Federal
  Court, 2000) The Accident Report had concluded: the probable causes
  of the accident were  related to failures of  the flight crew;
  contributing factor was related to FMS-generated navigational
  information; AA blamed the Jeppesen software in the  Honeywell
  computer; alleged that products  helped caused the crash; A Federal
  Jury found  that Jeppesen was  17% at fault and Honeywell 8 % at
  fault.

More: American Airlines Flight 965.


text:
Why is luggage required to be loaded in containers?
Luggage is loaded into containers, in Wide Body airliners (as mentioned here). Why is this required to be done? Why don't they simply keep the luggage in the luggage compartment? Why is loading the luggage piece-by-piece time consuming, and at the end, in second photo mentioned there, the luggage is being loaded piece-by-piece. What is that?

The link in this question already explains almost all points of the question. The only thing possibly unanswered is why some pieces of luggage (shown in the second photo) were not put in ULDs. The airline can easily manage a few pieces of luggage handled this way (compare the two photos: five ULDs on one conveyor vs. six individual pieces on the other!). But the added cost of handling all the luggage that way is well worth avoiding.

@DavidK The photos in the linked answers clearly show two different planes, not one plane being loaded partly with containers and partly with loose baggage. The first is a Japan Airlines 747 (actually being unloaded); the second appears to be a 737, in the livery of some airline that I don't recognize.

@DavidRicherby Good point; according to information from Boeing, passenger 737s don't use ULDs. Those are not just gate-checked bags, then. As far as I can tell, however, the answers below did not pick up on the difference between aircraft.

The central cargo hold is usually pretty big and open, if cargo was placed in loosely then it might shift in flight which can cause the center of mass to shift or damage the walls of the hold. Putting them in containers and fixing those down will prevent that.
The containers can also be weighed before hand and their position set to ensure the center of mass ends up where it should be. With loose cargo the pilot would need to rely on the intuition and experience of the loaders to ensure that they don't put all the heavy stuff on one side.
Loading loose luggage requires that the loader in the cargo hold handles each bag while stacking them. The hold also needs to be full enough that the luggage can't shift around.
The smaller forward and rear cargo holds (or on smaller planes) can still accommodate loose luggage (or more precisely they are too small for the containers to fit). They will also have netting to provide barriers against shifting.

You are right. Any steep takeoff at full power would send everything towards the back, leading to a rapid tail-heavy condition, stall, and crash.

If you want to see some tragic footage of what happens  when a load shifts: https://www.youtube.com/watch?v=lksDISvCmNI

@WayneWerner Sure but when your cargo is five military armoured vehicles, the effects aren't really comparable to a passenger plane full of people and their luggage.

Why is this required to be done?

As far as I know, this is not required by law, it is an operational practice by airlines. According to Wikipedia "It allows a large quantity of cargo to be bundled into a single unit. Since this leads to fewer units to load, it saves ground crews time and effort and helps prevent delayed flights."

Why don't they simply keep the luggage in the luggage compartment?

baggage can be loaded into ULDs while the aircraft they are intended for is still in flight. This reduces turn-around time. Aircraft only earn money when they are in the air, on the ground they bleed money from the airline's shareholders. Airlines try to keep aircraft in the air and avoid having them on the ground as much as possible.

Why is loading the luggage piece-by-piece time consuming

Because luggage is not of uniform size, shape and strength. Therefore it is a labour-intensive process not especially amenable to full mechanisation.
It simply takes longer to load 50 (say) randomly shaped objects than it does to load one object of standardised shape and size.

at the end, in second photo mentioned there, the luggage is being loaded piece-by-piece. What is that?

I don't know, but it seems plausible that some passengers are willing to pay for their luggage to be carefully hand loaded. I.e. first-class. This allows those passengers to pay for an express boarding process and spend less time in the airport.

baggage can be loaded into ULDs while the aircraft they are intended for is still in flight. That. Keeping aircraft on the ground costs money. Loading the cargo in larger containers up front saves time while loading the aircraft.

It's hard to tell but it looks like the second photo shows a B737 which is not a wide body and therefore does not have accomodation for ULD's in the belly.

@Mast then why do LCCs not universally use ULDs (or other containerised storage to include 737s here!), given they almost always have shorter turn-arounds than most wide-body aircraft?

@gsnedders Ask them, or ask a separate question on this SE. I don't know.

Well there are several advantages of loading the luggage in unit load devices (ULDs) such as:

In ULD, the luggage suffers much less shock than it would, if left alone. Else, the incidence of baggage manhandling would increase several times. We are already losing \$2.58 bn/year  due to this.
ULDs lead to better use of aircraft cargo space. Stacking the luggage one over the other would be a very time consuming and tiring job, and if it is not done, then a lot of cargo space of aircraft would be wasted. ULDs help prevent this.
ULDs are cost effective. Compare the cost of 100s people busy in stacking the luggage, and one conveyor belt doing the job.
ULDs are safer, in the way they prevent unauthorized access to the luggage.

And, in the second picture shown there, the luggage is being loaded into luggage hold. Which has several Pallets/Nets for storing small ammount of luggage. Usually, they are used to store some small cargo belonging to first class passengers.

I removed the mathjax to avoid unnecessary calls when loading the page.

I missed the 's' there! By CS, it's less time consuming because machines are doing the work while handling ULDs, and at last I am sorry because I can't provide you with any numbers regarding people needed to fill and load the ULDs.

Think about the benefits of containerisation.  Ships could take days to unload if they carried many different items like lumber, sacks of corn etc.  Along came containers and now you can unload a ship in hours.  The labour intensive part of loading/stacking is distributed toward the containers themselves, and thus frees up the expensive capital item such as a ship or plane to be turned around more quickly.  It all makes economic sense.  so is it required?  yes, if you wish to stay competitive and in business it is.

There are some safety and security aspects to containing luggage within containers. When content leaks, goes bad, or even explodes, the container may serve to limit the damage to other luggage within the aircraft, along with the aircraft itself.

The link is now dead but I'm skeptical about it mitigating explosions: explosions usually become more of a problem when they're confined.

Also, if the airline is feeding flights to other destinations, baggage can be pre-sorted. For example, a flight into CMB (Colombo, Sri Lanka) is commonly used as a feeder service for onward travel to MLE (Male, Maldives). If all the MLE-destination bags are separated from the CMB-destination bags at the time of loading and are in their own ULDs, those ULDs can be simply moved into the MLE aircraft, saving the time to offload all bags, re-sort and separate the MLE ones, and then reload.

authors: الباشق العدوان


text:
Why does this calculation show Gustave Whitehead's propellers were more than 100% efficient?
I have tried to calculate the efficiency of Gustave Whitehead's propellers using the information he provided to the American Inventor Magazine in 1902 (see the citation below).
Number of propellers = 2
Engine power per propeller, $P$ = 20 hp
Propeller diameter, $D$ = 6 ft
Static thrust per propeller, $T$ = 254 lbf
Propeller efficiency, $\eta_{prop}$
Gear efficiency, $\eta_{gears}$ < 100%
Air density, $\rho=1.2 \frac{kg}{m^3}$
Doing the calculations: $\eta_{prop} > \sqrt{\frac{T^3}{(P^2 \cdot \pi \cdot \eta_{gears} \cdot \frac{D^2}{2} \cdot \rho )}} = 101.4\%$ which is impossible.
Is there a mistake? If yes, where?
Note: I used the formula that relates static thrust to efficiency, power and propeller diameter.

The Whitehead Flying Machine
Has the End been Finally Attained, and is the Dirigible Balloon to Go?
Editor, American Inventor
Dear Sir: Replying to your recent letter, I take pleasure in sending you the following description of my flying machine No. 22, the latest that I have constructed:
This machine was built in four months with the aid of 14 skilled mechanics and cost about $1,700 to build. It is run by a 40 horse-power kerosene motor of my own design, especially constructed for strength, power and lightness, weighing but 120 pounds complete. It will run for a week at a time if required, without running hot, stopping, or in any possible manner troubling the operator. No electrical apparatus is required for ignition purposes. Ignition is accomplished by its own heat and compression; it runs about 800 revolutions per minute, has five cylinders and no fly-wheel is used. It requires a space 10 inches wide, 4 feet long and 10 inches high. ...
The propellers are 6 feet in diameter and have a projecting blade-surface of 4 square feet each. They are made of wood and are covered with very thin aluminum sheeting. The propellers run about 600 revolutions per minute under full power and turn in opposite directions. When running at full speed they will exert a thrust of 508 pounds. I measured this thrust by attaching the machine to a post by means of a dynamometer and running the engines at full speed. ...
I have no photographs taken yet of No. 22, but send you some of No. 21, as these machines are exactly alike, except the details mentioned. No. 21 has made four trips, the longest one and a half miles, on August 14, 1901.   The wings of both machines measure 30 feet from tip to tip, and the length of the entire machine is 32 feet.   It will run on the ground 50 miles an hour, and in air travel at about 70 miles.  I believe that if wanted it would fly 100 miles an hour. The power carried is considerably more than necessary. ...
Trusting this will interest your readers, I remain, Very truly yours,
GUSTAVE WHITEHEAD
Bridgeport, Conn.

Source: The American Inventor Magazine
, 1 April 1902
.

The value you use for air density is probably too low. Whitehead is reporting on an actual experiment probably performed in cold weather. Also he makes no mention how he measured P. or indeed if he did. It is possible he just worked back from the thrust by assuming 100% efficiency. Also you did note the letter is dated April 1?

Even if I use the air density for -25 C, 1.42 kg/m^3, I still get an efficiency of 93.2% which is too big. 2) Whitehead says in the article that he was the one who designed the engine. If he was capable to design such a motor it is unbelievable he was incapable to determine its power. In order to have worked back the power from the thrust he must have known the formula I mentioned and in this case he would not have used an efficiency of 100% as long as the propellers of the time were around 50% efficient.

Basically, I find it very hard to believe that the power of an experimental, self designed and largely built (?) engine would just happen to be a round number. And it does not actually say he meant shaft horsepower. In fact given that he designed the whole system, what reason would he have for reporting the power of engines separate from the transmission and propellers they were built for?

He could have meant effective power converted to thrust, I suppose. It would match the numbers pretty good and solve your puzzle.

Ville Niemi, It is hard to follow you. What do you mean by "effective power converted to thrust"? This seems equivalent to using an engine much powerful than 40 hp, around 80 hp, weighing just 120 pounds, in 1902?! If you have an explanation try to find a mathematical form for it.

Yes, you understood my meaning just fine. And I find it hard to believe myself. Then again he is claimed to have built a 200hp engine in 1903...

When I did it, I got an efficiency of 81%. See https://aviation.stackexchange.com/a/84902/54471

The term horsepower was used in some contexts to relate to 150cc capacity (for example the Douglas 4hp motorcycle).  However, 40hp in this context would equate to a 6 litre capacity.  At 800rpm that’s perhaps not a huge stretch of the imagination?

As you present it, you are right and Whitehead's numbers are impossible.
I doubt that he could measure engine power with enough precision, and who knows what definition for horsepower he used. Power measurement needs some heavy machinery, and Whitehead most likely did not own a suitable dynamometer. It would be interesting to know the fuel consumption of this engine - that could help to check his numbers better.

What I know is that a previous engine of Whitehead, used in 1901, delivered 30 HP and needed 60 pounds of fuel to run for 6 hours (see: The flight apparatus of Gustave Whitehead) page 6-7.

@RobertWerner: Thank you, that helps. A standard gasoline engine with carburetor consumes 280 g of fuel per KW and hour. 10 pounds for 30 HP are 202 g per KW - either Gustave did not run the engine on full power, or his consumption figure is unbelievably low. Now we have the opposite situation where the power output is too high for the given conditions. Could it be that Gustave rounded the numbers to his advantage?

@RobertWerner: Now I read that these figures are for the calcium carbide-acetylene engine, so a direct comparison to a gasoline engine is not possible.

Heat of combustion for acetylene = 49.9 MJ/kg, for gasoline = 47 MJ/kg (see: Heat of combustion). The difference is small.

The equation you referenced shows prop diameter squared, divided by 2, not 4.
Even then, the calculation shows that marketing is to experimentation as about 2:1 :)

Streak, Yes you are right. It is D^2/2 not D^2/4. With your correction the efficiency gets lower, 101.4%, but it still stays above 1 which is not possible. I will correct the question. Thank you for your answer.

Example of two ~static thrust tests
1) Engine: C-85-12 Continental (85hp, redline 2575rpm)
Propeller: McCauley 71×46 Met-L, aluminum (This is a climb prop for a 120)
Wind: 4-9mph headwind
Performance -- Thrust: 340 pounds, RPM: 2350
Propeller efficiency: ~ 37.5%
2) Engine: Continental O-200, 100hp, 2750rpm redline
Propeller: McCauley Clip Tip 68″ diameter, aluminum, standard pitch
Wind: 5-7mph headwind
Performance -- Thrust: 335 pounds, RPM: 2332
Propeller efficiency: ~ 32.5%
see: Thrust testing 85 and 100 hp engines
Note: The efficiency was calculated using the formula: $\eta_{prop} = \sqrt{\frac{T^3}{(P^2 \cdot \pi \cdot \eta_{gears} \cdot \frac{D^2}{2} \cdot \rho )}}$
Conclusion:
If the formula for $\eta_{prop}$ is reliable it seems that a modern propeller has a rather poor efficiency during a static thrust measurement. Gustave Whitehead might have optimized his aerial screws for supplying maximum static thrust possible but even in this case he could not have obtained an efficiency above 90%.

Whitehead's claims for his engine are difficult to believe. According to his description it was a five-cylinder Diesel (compression-ignition) running on kerosene. It would have needed a high compression ratio with fuel injection. That in turn means strong, heavy cylinders. It makes interesting comparison with the successful spark-ignition Antoinette V8 of a few years later:

Length: Whitehead 48 in, Antoinette 44 in
Width: Whitehead 10 in, Antoinette 25 in
Height: Whitehead 10 in, Antoinette 21 in
RPM: Whitehead 800, Antoinette 1,100

It is clear that Whitehead's cylinders could not have been significantly bigger than the 1.0 L of the Antoinette's, and there were only 5 instead of 8 of them. And his engine revolved more slowly. Yet he claims 80% of the power output. This is perfectly possible if his compression ratio is much higher. But here we come to the crunch:

Weight: Whitehead 120 lb, Antoinette 209 lb.

As a crude comparison based on cylinder count, 5/8 of 209 = 130.6. So his claim implies a cylinder weight no greater than the Antoinette's, yet capable of withstanding far higher pressures.
Junkers later built two-stroke Diesels, developing high output per cylinder as the compression was not only high but you got a bang every revolution instead of every other. The 12-piston (in 6 cylinders!) Jumo 204 produced 590 hp at 1,600 rpm. At Whitehead's 800 rpm, half the 204's revs, that corresponds crudely to half the power, or around 300 hp. It weighed 1,653 lb giving, at 800 rpm, a mere 22 hp per 120 lb, half Whitehead's claim - and that not until 1929.
So either Whitehead was a total genius at Diesel engine design, with access to remarkably high-quality materials and advanced manufacturing technology, or somebody in the food chain has embellished the truth. He did earn his living at the time, and paid for his experiments, by making and selling aero engines, and in this he appears to have had a reputation for first-class workmanship, but even so....

I used the formulas from my answer to What is the correct formula to calculate propeller efficiency? and arrived at the following:
we have:

$\beta$=0,
$P$= 20 hp=14,914 W,
$D$=6 ft=1.8±0.3 m,
$T$= 254 pounds=1130 N,
$\rho=1.2 \rm\ kg/m^3$, yielding

$$T_0=\left[\pi\times 1.2\times 14,914^2\times 1.8^2\right]^{1/3}\rm N=1,395±232\ N,$$ with a propeller efficiency of $\eta_{\rm P}$=(1,130/1,395)=81±13%, which seems to me to be a reasonable efficiency.

Let us continue this discussion in chat.

Arthur Tayler, welcome to aviation.stackexchange. I can't see the other answer you refer to, also not as deleted question (I have access to part of the moderator tools ). Something must have gone wrong when you submitted it. As it stands, this answer is a 'link-only' answer, which will likely be deleted by the community. Please include the calculation you did in your answer here (you can keep the link; it is fine as support).

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.  Link-only answers can become invalid if the linked page changes. - From Review

My view is #1 that repetition is bad, so it would be bad to have the duplicated parts you require here. #2 I don't agree with your def of "link only" since I show the answer.  For me to copy parts of the other answer duplicates content which is against Jeff Atwood's vision that less is more.  Moreover, while I could state the obvious, (the answer isn't >100% in the first place), it would again be against Atwood's vision.  So, it seems no matter I do you'll delete. And the link change argument basis was really about off-site content, not inherent SE content.

If you allow me, would like to edit both of your answers and move the part that is relevant to this question from the other answer to here. And include a link in the other answer to this answer.

I made the edit so that the part relevant to this question is included in here, the formula and every else remain in the original question. This way, 1) your work doesn't get lost, 2) your answer here will likely survive. If you disagree you may always rollback my edits.

ymb, thanks for the link.  I 100% agree with the view that context to links is important. About me deleting my own answer, the threat isn't that I'd delete my own answer, it's that you guys delete it.  And, now, if either answer gets deleted then neither answer is any good.  With a -2 on one answer and a 0 on the other, I'm expecting both will be gone before I dare come to SE again for more abuse.